Steel caps with two screws per side provide extra strong, 4-screw, clamping power. Helps ensure that reticle stays square while tightening top screws. Large clamp nut locks rings to base, provides easy scope installation, removal; and accurate return to zero after re-installation. Mfg: Weaver SPECS: Aluminum lower; steel cap, screws, crossbolt and nut. Black, gloss or matte finish. Heights (above base): 1" (2.5cm) diameter - Med., .164" (4.16mm); High, .332" (8.43mm); X-High, .560" (14.2mm).